Study notes on Locomotion and Movement

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Study notes on Locomotion and Movement

Movement is a change in posture or position. It is an essential and significant feature of living organisms and hence both unicellular and multicellular organisms show movement. Organisms show different structures such as cilia, flagella, pseudopodia limbs, jaws, eyelid, tongue etc. for movement.

The movement which result in the change of place or location are called locomotion.

MOVEMENTS OF BODY PARTS

Both the internal and external structures of an organism (constituted by cell and intracellular structures) show movements.

Movements of External Body Parts

The external body parts show movement essential for various aspects of the organism.

  • To maintain the equilibrium of the body- limbs, head, trunk etc. play animportant role.
  • The movement of limbs, appendages, jaws, tentacles, tongue in organisms helps to capture food.
  • Movement of limbs is responsible for ingestion, defence, locamotion etc.

Movements of Internal Body Parts

The movement of internal body parts are also essential for functioning of various cells, tissues and organs of the body. They help the organism to carry out vital processes of the organisms such as :

  • The food from the mouth moves to the stomach for digestion through the peristaltic movement of the oesophagus.
  • Pumping of heart for circulating blood to different parts of the body.

Types of Movements

On the basis of structure, three basic types of movernents occur in the cells of human body namely amoeboid, ciliary and muscular

Amoeboid or Pseudopodial Movements

  • Due to the streaming of protoplasm or cytoplasm, the surface of the cell forms false feet or pseudopodia.
  • As Amoeba, WBÇ, and macrophages show pseudopodial movements they do not have a fixed shape.

Cilary Movements

  • The free surface of the cells have short fine hair-like projections called cilia.
  • The movement of these projectións (cilia) is called ciliary movement.
  • Coordinated movement of cilia in trachea helps in the removal of dust particles inhaled along with atmospheric air.
  • Passage of ova through the female reproductive tract is also facilitated by the ciliary movement.

Muscular Movement

  • In humans, movement of limbs, jaw, tongue and other body parts occur due to contraction of muscles.
  • The muscles contract and relax rhythmically to produce movement and are usedeffectively for locomotion.

MUSCLES

  • Muscle is a specialised tissue originated from the germ layer, mesoderm.
  • The muscular tissue is made up of specialised cells called myocytes.
  • These cells are bounded together by a connective tissue and form muscular tissue.
  • It brings about different types of movements in internal and external body parts.
  • A human body is made up of 639 muscles which have unique properties like contractibility, excitability, elasticity and extensibility.
  • They make about 40-50 percent of body weight in adult human.
  • The myocytes have an ability to contract. They can shorten by 1/3 to 1/2 of their length due to contraction and then return to its original length, called contractility.

Study notes on Locomotion and Movement

diagrammatic cross sectional view of a muscles showing the muscle bundles and muscle fibres

Structure of Muscle

  • A muscle is covered by a sheath of connective tissue called
  • Inside the epimysium, a muscle has many muscle fibres arranged in a bundle called fasciculi (singular-fasciculus or fascicle).
  • Each fasciculus is surrounded by a sheath of connective tissue called
  • The muscle fibres are parallel to each other in the fasciculus and is surrounded by a connective tissue called endomysium.
  • The muscle bundle are further bounded together by a common collagenous sheath of connective tissue called fascia.
  • Tendons: The two ends of the muscles are attached to the bone with the help of an inelastic connective tissue called tendon.

Study notes on Locomotion and Movement

Difference between Striated, Smooth, Cardiac Muscle

Striated or Skeletal Nonstriated or Smooth or Visceral Cardiac
These are cylindrical. These are spindle-shaped. These are cylindrical.
Their ends are blunt. Their ends are tapering Their ends are blunt.
Fibres are unbranched. Fibres are unbranched. Fibres are branched.
Fibres occur in bundles. They occur singly, in sheets and small budles They form three-dimensional
Blood supply is abundance. Blood supply is poor They are rich in blood supply.
Voluntary. Involuntary. Involuntary.
They are innervated by branches from cranial and spinal nerves They are innervated by autonomic nervous system. They are innervated by autonomic nervous system.
Intercalated disc is absent. Intercalated disc is absent. Intercalated disc is present.
These fibres are multinucleated/syncytial. uninucleated. uninucleated.
Mitochondria are moderately abundant. Mitochondria are fewer Mitochondria are abundant
Myoglobin is abundant. Myoglobin is poor Myoglobin is abundant.
They contract quickly. They contract slowly.

 

They Show rhythmic contractions.
They do not fatigue. They do not fatigue. They do not fatigue.

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Ultrastructure of striated Muscle

  • Skeletal muscle consists of many muscle fibres, anatomical unit of muscle, Muscle fibre is covered by a plasma membrane called sarcolemma.
  • The sarcolemma encloses the sarcoplasm which contains many nuclei.
  • The muscle fibres contain parallelly arranged myofibrils which have the alternate light and dark bands.
  • The sarcolemma invaginates to form T-tubules , transverse tubules.
  • These T-tubules are formed over the myofibrils(like a curtain).
  • A single myofibril is made up of two types of myofilaments- thick myofilament and thin myofilament.
  • The thick myofilament consists mainly of myosin protein and the thin myofilament consists of mainly actin
  • The endoplasmic reticulum present in the sarcoplasm is called sarcoplasmic reticulum.
  • It is the store house of calcium required during muscle contraction.
  • The dark band present on the myofibril is called ‘A-band’ or anisotropic band and the light band present on the myofibril is called l-band or Isotropic band.
  • At the center of the dark A-band, a comparatively lighter area called ‘H-band’ or Hensen’s zone is present.
  • A dark M-line passes through the centre of H-band.
  • The light I-band consists of, a dark line which passes through the centre called Z-line.
  • The part of myofibril between the two successive Z-line is called sarcomere.
  • The sacromere is the structural and functional unitof myofibril.
  • A sarcomere hence comprises of a single A-band and half of each adjacent l-band.

Study notes on Locomotion and Movement

Structure of Contractile proteins

Thick myofilament

  • The thick myofilaments are made up of polymerised protein called myosin.
  • The monomeric proteins called meromyosins polymerised to form the myosin protein.
  • Each meromyosin has two parts- a globular head with a short arm and a tail.
  • The globular head along with the short arm is called heavy meromyosin (HMM), and the tail is called light meromyosin (LMM).
  • The globular head has a site for binding of actin and ATP, The globular head act as an ATPase enzyme. It hydrolyses ATP to produce energy.
  • Each myosin moleculeş forms a tadpole-like structure where the tails of the molecules are joined to form the body of the myosin filament. Heads and the short arms protrude out of the body and makę cross-bridges with actin.

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Study notes on Locomotion and Movement

 

Thin filament

The thin myofilament is made up of three proteins- actin, tropomyosin and troponin.

  • Actin: Actin is a globular protein, which has a low molecular weight. It occurs in two forms monomeric G actin and polymeric F-actin. The G-actin polymerises to form the F-actin in the presence of magnesium ion.
  • Tropomyosin: Tropomyosin is a fibrous molecule. The two filaments of tropomyosin run closely along the entire length of the acțin. At resting state it separates the actin and myosin by binding to the myosin binding site on actin filament and hence prevents the formation of cross bridges which in turn prevents the contraction of muscle fibre.
  • Troponin: At regular intervals of tropomyosin, a complex protein called troponin is present. It masks the active binding sites for myosin on actin filament. A troponin is a trimeric protein i.e., it has three units which acts as the binding sites for three different components. The three units of troponin are :
  1. Troponin I: It iphibits actin-myosin interaction and binds to other components of troponin.
  2. Troponin T: It is the binding site for tropomyosin
  3. Troponin C : It is the binding site for calcium.

MECHANISM OF MUSCLE CONTRACTION

The mechanism of muscle contraction is explained by a theory called sliding filament theory.According to this theory, the contraction of muscle fibre occurs when thin filament ie. actin filament slides over thick filament i.e., the myosin filament

  • The contraction of the muscle is initiated by the signal sent by CNS via a motor neuron.
  • The nerve impulse given by the CNS travels through the motor neuron.
  • When the impulse reaches the axon terminal or neuromuscular junction, vesicles containing neurotransmitters fuses with the axon membrane.
  • After fusion with the axon membrane they release the neurotransmitter, acetylcholine, which travels through synaptic cleft and generate action potential in the sarcolemma.
  • The impulse or action potential generated then spread from sarcolemma to the T-tubules.
  • The impulse then stimulates the sarcoplasmic reficulum to release calcium ion into the sarcoplasm.
  • An increase in Ca2+ concentration in the sarcoplasm starts filament sliding, while a decrease turns off the sliding process.
  • When a muscle fibre is relaxed (not contracting), the concentration of Ca in its sarcoplasm is low. This is because the sarcoplasmic reticulum (SR) membrane contains Ca2+ active transport pumps that move Ca from the sarcoplasm into the SR.
  • Ca²+ is stored or sequestered inside the SR.
  • As a muscle action potential travels along the sarcolemma and into the transverse tubule system, however, Ca2+ release channels open in the SR membrane.
  • As a result, Ca2+ floods into the sarcoplasm around the thick and thin filaments.

Study notes on Locomotion and Movement

stages in cross Bridge formation rotation of head and breaking of cross bridge

  • The globular head of myosin acts as an ATPase and hydrolyses ATP molecule. The energy derived from the hydrolysis of ATP is used by myosin to bind the exposed active site on actin filament to form a cross bridge.
  • This pulls the actin filament (attached) towards the centre of ‘A-band’.
  • The Z-line attached to these actinsare also pulled inwards thereby causing a shortening of the sarcomere i.e., contraction.
  • The thin myofilaments move past the thick myofilament due to which the H-zone narrows. This reduces the length of l-band but retain the length of A-band.
  • The myosin then release ADP+Pi, and goes back to its relaxed state. Again the ATP binds to the myosin and connection or cross bridge between myosin and actin is broken.
  • The ATP is again hydrolysed and.the cycle of formation and breakage of cross-bridges is repeated causing sliding.
  • The process continues till the calcium ion is pumped back into the sarcoplasmic reticulum. This causes the return of ‘Z’ lines back to their original position i.e., relaxation occurs.

Study notes on Locomotion and Movement

MUSCLE RELAXATION

  • After the contraction of muscle, the calcium moves back into the sarcoplasmic reticulum. The amount of calcium in the sarcoplasm decreases due to which the calcium does not bind to the troponin C.
  • The troponin undergoes change in shape and the tropomyosin and troponin attain their earlier position and state.
  • This blocks the active site of myosin on actin, and myosin does not bind to actin. This causes relaxation of muscle.

MUSCLE FATIGUE

Repeated activation of the muscles can lead to the accumulation of lactic acid due to anaerobic breakdown of glycogen in them, causing fatigue.

RED AND WHITE MUSCLE FIBRES

  RED MUSCLE FIBRES    WHITE MUSCLE FIBRES
Myoglobin content is high, so it is red Myoglobin content is low, so it is pale
Mitochodria is more in number Mitochodria is less in number
Depends on aerobic process of energy Depends on anaerobic process of energy
Sacroplasmic reticulum is less extensive Sacroplasmic reticulum is more extensive
Contraction is less powerful Contraction is more powerful

HUMAN SKELETON

  • Skeletal system consists of a framework of bones and a few cartilages. This system has a significant role in movement shown by the body.
  • Bone and cartilage are specialised connective tissues.
  • The former has a very hard matrix due to calcium salts in it and the latter has slightly pliable matrix due to chondroitin salts
  • In human beings, this system is made up of 206 bones and a few cartilages. It is grouped into two principal divisions – the axial and the appendicular skeleton.

Axial Skeleton

Skull

  • Skull bones and associated bones are 29 in number
  • The skull is composed of two sets of bones – cranial and facial, that totals to 22 bones.
  • Cranial bones are 8 in number. They form the hard protective outer covering cranium for the brain.
  • The facial region is made up of 14 skeletal elements which form the front part of the skull.
  • A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull.
  • Each middle ear contains three tiny bones – Malleus, Incus and stapes, collectively called ear ossicles.
  • The skull region articulates with the superior region of the vertebral column with the help of two occipital condyle(dicondylic skull).

(i)Cranium – 8

(ii)Face – 14

(iii)Ear ossicles -3 +3 = 6

(iv) Hyoid – 1

  • All skull and associated bones (except mandible and ear ossicles) are immovable.

Study notes on Locomotion and Movement

Cranium

  • It encloses the brain. It has large opening called foramen magnum. Human skull is dicondylic (with 2 occipital condyle).
  • Cranium formed of 8 bones (membranous bone)

1 Frontal (forehead)

1 Occipital

2 Temporal

1 Ethmoid

2 Parietal

1 Sphenoid

All these bones of skull are joined together by suture.

Cranium Bones – [8]

Frontal bone [1] : It is in the anterior or frontal part at the top of cranium. It forms the forehead and some upper parts (roofs) of eye sockets.

Parietal bones [2] : Situated just behind the frontal bones. They forms the roof of cranium and maximum part of side of cranium.

Occipital bone [1]: Situated just behind parietal. On each side of this foramen one condyle is present called as occipital condyle. So the human skull is dicondylic.

Temporal bones [2] : Forms the lower parts of each sides of cranium. In the house of this bone intemal and middle ear are present. The middle ear of each side encloses three small bones – Malleus, incus, stapes.

Sphenoid bone [1] : A butterfly shaped bone which forms middle and anterior part of base of cranium.

Ethmoid bone [1] : A small irregular bone infront of sphenoid and behind nasal bones.

 

Facial – Bones [14]    

Nasal bones [2] : Small, rectangular bones which forms dorsal surface of nasal chambers.

Inferior turbinals (2] : Situated on lateral surface of nose.

Vomer [1] : A thin plate like bone present is posterior part of nasal chambers.

Lacrimals [2]: Smallest bones of face. Each located in the lateral sides of nasal bones. These bones form a part of the wall of eye sockets.

Zygomatics or malar bones [2] : Also called as cheek bones.

Palatines [2] : ‘L’ shaped bones that form the back (posterior) part of our hard palate.

Maxillary [2]: Large, upper jaw bones that form the major part of our face and upper jaw comprise anteriorpart of our hard palate. Teeth of upper jaw are fit in the cavity of this bone.

Mandible [1] :Largest and single bone of lower jaw. It is largest bone of face and strongest bone of axial skeleton of body.

Hyoid bone [1] (Tongue bone)

It is single U shaped bone which is present at the base of buccal cavity. It is not articulated to any bone of axial skeleton. The muscles of tongue, larynx, neck and parynx are attached with this bone.

Vertebral column

Study notes on Locomotion and Movement

vertebral column(lateral view)

  • Our vertebral column is formed by 26 serially arranged units called vertebrae and is dorsally placed
  • It extends from the base of the skull and constitutes the main framework of the trunk.
  • Each vertebra has a central hollow portion (neural canal) through which the spinal cord passes.
  • First vertebra is the atlas and it articulates with the occipital condyles
  • The vertebral column is differentiated into cervical (7), thoracic (12), lumbar(5), sacral (1-fused) and coccygeal (1-fused) regions, starting from the skull.
  • The number of cervical vertebrae are seven in almost all mammals including human beings.
  • The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back.
  • Sternum is a flat bone on the ventral midline of thorax.

RIBS

Study notes on Locomotion and Movement

Ribs and Rib cage

  • Total 12 pairs ribs are present in Human.
  • Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum.
  • Rib has two articulation sarfaces on its dorsal end and is hence called as bicephalic.
  • First 7 pairs of ribs called True Ribs. (Vertebrosternal ribs) Dorsally, they are attached to the thoracic vertebrae and ventrally connected to the sternum with the help of hyaline cartilage.
  • Remaining 5 pairs are False Ribs, The 8th, 9th and 10th pairs of ribs donot articulate directly with the sternum but join the seventh rib with the help of hyaline cartilage. These are called vertebrochondral ribs.
  • Last two pairs (11h and 12th) of ribs are not connected ventrally and are therefore, called floating ribs.
  • Thoracic vertebrae, ribs and sternum together form the rib cage.
  • Head of rib has two parts. Lower part articulates with numerically corresponding vertebrae
  • Upper part articulates with higher vertebrae.

Appendicular skeleton

  • The bones of the limbs alongwith their girdles constitute the appendicular skeleton.
  • Each limb is made of 30 bones.
  • The bones of the hand (fore limb) are humerus, radius and Cervical vertebra,ulna, carpals (wrist bones – 8 in number), metacarpals (palm bones – 5 in number) and phalanges (digits – 14 in number)
  • Femur (thigh bone – the longest bone), tibia and fibula, tarsals (ankle bones – 7 in number), metatarsals (5 in number) and phalanges (digits – 14 in number) are the bones of the legs (hind limb)
  • A cup shaped bone called patella cover the knee ventrally (knee cap)

Pectoral girdle

Study notes on Locomotion and Movement

  • Bones help in the articulation of upper limbs with the axial skeleton.
  • Pectoral girdle is formed of two halves.
  • Each half of pectoral girdle consists of two bones i.e. Scapula + Clavicle
  • Scapula : It is a large, triangular flat bone, It is situated in the dorsal part of the thorax between the 2nd and 7th ribs. It has 3 process which provide attachment to muscles –

– Spinous process

– Acromion process

– Coracoid process

  • Clavicle (Collar Bone) is a weak, thin, cylindrical bone with two curvatures (ends).
  1. Medial End : Articulates with the clavicular notch of
  2. Lateral End : Bears a facet which articulates with acromion process of scapula.

Pelvic girdle (Hip bone)

Study notes on Locomotion and Movement

  • Bones help in the articulation of lower limbs with the axial skeleton.
  • Also called as innominate.or coxal bone.
  • Each coxal bone is formed by fusion of three bones Ilium, Pubis and Ischium.
  • Pubis & ischium are separated by a large opening (=obturator foramen),
  • At the point of fusion of above bones is a cavity called acetabulum to which thigh bone articlate.
  • Two halves of the pelvis girdle meet ventrally toform the pubic symphysis containing fibrous cartilage.
  • Pelvic diameter is larger & more circular in femalethan male to accomodate the foetus during pregnancy

JOINTS

Joints are points of contact between bones or between bones and cartilages. Force generated by the muscles is used to carry out movement through joints.

(A) STRUCTURAL CLASSIFICATION

(I)Fibrous Joints

  • It do not allow any movement.
  • This type of joint is shown by the flat skull bones which fuse end-to-end with the help of dense fibrous connective tissues in the form of sutures, to form the cranium.

(II) Cartilagenous Joints

  • It is slightly movable
  • It is also called as amphiarthroses.
  • The bones involved are joined together with the help of cartilages.
  • The joint between the adjacent vertebrae in the

vertebral column is of this pattern

 (III) SYNOVIAL JOINTS

  • It is highly mobile
  • It is also called as Diarthrosis.

(1)Plain synovial or gliding joint

permit slight gliding movement e.g., joint between z carpals, between tarsals

 (2) Hinge Joint

Movements are permitted in one plane around transverse axis e.g. elbow joint, ankke joint, knee joint.

(3)Pivot Joint

a central bony pivot e.g. radioulnar joint,

(4) Condylar joint

Articular surface include two distinct condyles Movement are permitted in both transverse & vertical axis. rt & left – jaw joint, knee joint

(5) Ellipsoid joint

Movement are permitted in both axis, but articular surfaces are not in form of condyles. e.g. wrist joint

(6)Saddle Joint

e.g. first carpometacarpal joint. (between carpal and metacarpal of thumb.)

(7)Ball & socket joint

Here one articular surface is like a ball and other of the shape of socket.

Movements are around infinite axises. e.g. shoulder & hip joint.

Disorders of Bones

  • Myasthenia gravis: Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of skeletal muscle.
  • Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.
  • Tetany: Rapid spasms (wild contractions) in muscle due to low Ca++in body fluid.
  • Arthritis: Inflammation of joints.
  • Osteoporosis: Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause.
  • Gout: Inflammation of joints due to the accumulation of uric acid crystals.

REFERENCES

  1. https://ncert.nic.in/ncerts/l/kebo120.pdf